Aerodynamic Optimization of In-Line and Parallel Layouts for Symmetric Cambered Wingsail Installation

Rigid wingsails are an established design for thrust generation on large commercial ships. Specifically, efficiency improvements have been found for wingsails with sectional profiles using a camber that is symmetric about the middle of the chord. This study aims to identify effective installation layouts for multiple wingsails to maximize practical thrust generation. Aerodynamic interference effects among the wingsails are computed using a fast 2D potential-flow method, which is validated against previous 3D high-fidelity simulation data in terms of lift and drag forces. Two typical layouts are considered, that is, triple sails arranged in line (TL) and quad sails in parallel (QP). The layouts are optimized using the genetic algorithm, with the objective to achieve the largest thrust at apparent wind angles (AWAs) of 60°, 90°, and 120°. The optimized parameters are the distances between the sail units with a constraint of the total distance. Then, the optimization results are analyzed to understand how the distances affect lift and drag forces, as well as the pressure distributions on the sails. As found in other studies in general, the thrust generation decreases from the upstream sail to the downstream ones. The reason is mainly associated with locally induced AWA. Additionally, the optimal distances should be determined by analyzing the aerodynamic performance at different wind conditions instead of simply at a specific AWA. Unfavorable and favorable conditions for the thrust generation are also discussed. It was found that the QP layout significantly reduces the thrust generation compared to the TL layout. The findings provide insights into installation layouts for the thrust generation from multiple wingsails.